Question

我创建了两个表， simplecomments 和评论员，并将它们与INNER JOIN相关联。

简单评论是每个评论者的详细信息，涉及他们的评论，reg_date，commentorid等......
评论者是评论者的个人信息，其中包含以下列：id，name，email ..

我已经成功加入了它们，但是我发现很难从连接表中删除它。

我想让它像这样的逻辑：

如果，评论员的最后一行称为--let说A--然后从表中删除他/她的评论详细信息和A他/她自己。
其他如果A已经多次发表评论，发表不同评论，请删除他/她的评论详情，但是由于A还有其他评论，所以请保留他/她的个人信息。

这就是我的成就：

if (!empty($_POST["delete"]))
{
    foreach ($_POST["delete"] as $key => $value) 
    {
        $resultid = $conn->query("SELECT commentorid FROM `simplecomments` WHERE id=".$value);
        $rowid = $resultid->fetch_assoc();

        $outputdelete = $rowid["name"] . " has been deleted" . "<br>";

        $deletedname = $deletedname.$outputdelete;
        $RES = mysql_num_rows($resultid);
        $counter = 0;
            while($row = $RES)
            {
               //IF IT'S LAST ROW, DELETE COMMENTOR AND HIS/HER COMMENTDETAILS 
                if(++$counter == $results) {
                    $resultid = $conn->query("DELETE FROM `commentor`");
                }
                //ELSE JUST DELETE HIS/HER COMMENTDETAILS, LET HIS/HER INFO REMAIN
                else{
                    $resultid = $conn->query("DELETE FROM `simplecomments` WHERE id=".$value);
                } 
            }
    }

}

但是代码不起作用。我收到一个错误：

警告：mysql_num_rows（）期望参数1为resource [..] ...

Answer 1

考虑使用子查询条件运行DELETE...INNER JOIN和DELETE，并避免使用if/else进行PHP查询获取循环，因为逻辑似乎如下：

删除任何评论员的个人资料和评论，如果他/她只有一个评论
如果他/她有多个（即多个）评论，则只删除评论员的评论。

是的，所有三个DELETE都可以在所有ID上同时运行，因为在前两个和最后一个之间存在互斥条件。因此，前两个影响行，或者最后一个影响每次迭代的行。未受影响的人将从任一表中删除零行。

此外，首先删除 simplecomments 记录，因为由于其一对多关系，此表可能与 commentor 具有外键约束。最后，下面假设 comment id传递给循环（不是 commentor id）。

PHP （使用参数化，假设$ conn是mysqli连接对象）

foreach ($_POST["delete"] as $key => $value) {

   // DELETE COMMENTS AND THEN PROFILE FOR COMMENTORS WITH ONE POST    
   $sql = "DELETE FROM `simplecomments` s 
           WHERE s.id = ?
             AND (SELECT COUNT(*) FROM `simplecomments` sub
                  WHERE sub.commentorid = s.commentorid) = 1";
   $stmt = $conn->prepare($sql);
   $stmt->bind_param("i", $value);
   $stmt->execute();
   $stmt->close();

   $sql = "DELETE c.* FROM `simplecomments` c 
           INNER JOIN `simplecomments` s ON s.commentorid = c.id
           WHERE s.id = ?
             AND (SELECT COUNT(*) FROM `simplecomments` sub
                  WHERE sub.commentorid = s.commentorid) = 1";
   $stmt = $conn->prepare($sql);
   $stmt->bind_param("i", $value);
   $stmt->execute();
   $stmt->close();


   // DELETE COMMENTS FOR COMMENTORS WITH MULTIPLE POSTS BUT KEEP PROFILE
   $sql = "DELETE FROM `simplecomments` s
           WHERE s.id = ?
             AND (SELECT COUNT(*) FROM `simplecomments` sub
                  WHERE sub.commentorid = s.commentorid) > 1";    
   $stmt = $conn->prepare($sql);
   $stmt->bind_param("i", $value);
   $stmt->execute();
   $stmt->close();
}

或者，对于DRY-er方法，在数组中循环SQL语句：

$sqls = array(
           0 => "DELETE FROM `simplecomments` s WHERE s.id = ? AND (SELECT COUNT(*) FROM `simplecomments` sub WHERE sub.commentorid = s.commentorid) = 1",
           1 => "DELETE c.* FROM `simplecomments` c INNER JOIN `simplecomments` s ON s.commentorid = c.id WHERE s.id = ? AND (SELECT COUNT(*) FROM `simplecomments` sub WHERE sub.commentorid = s.commentorid) = 1",
           2 => "DELETE FROM `simplecomments` s WHERE s.id = ? AND (SELECT COUNT(*) FROM `simplecomments` sub WHERE sub.commentorid = s.commentorid) > 1"
        );

foreach ($_POST["delete"] as $key => $value) {
   foreach($sqls as $sql) {
       $stmt = $conn->prepare($sql);
       $stmt->bind_param("i", $value);
       $stmt->execute();
       $stmt->close();
   }
}

删除内部联接的行

1 个答案: